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GCN Circular 30984

Subject
GRB 211024B: Nanshan/NEXT optical afterglow detection
Date
2021-10-25T01:27:33Z (2 years ago)
From
Dong Xu at NAOC/CAS <dxu@nao.cas.cn>
Z.P. Zhu (NAOC, HUST), S.Y. Fu, X. Liu, D. Xu (NAOC), X. Gao (Urumqi 
No.1 Senior High School), J.Z. Liu (XAO) report:

We observed the field of GRB 211024B (Gropp et al., GCN 30980) using the 
NEXT-0.6m optical telescope located at Nanshan, Xinjiang, China. 
Observations automatically started at 22:23:13 UT on 2021-10-24, i.e., 
157 s after the BAT trigger. A series of 3x40 s, 3x60 s and 12x90 s 
frames in the Sloan r-filter were obtained.

An uncatalogued evolving optical transient is detected within the 
Swift/BAT error circle (Gropp et al., GCN 30980), at coordinates

R.A. =  10:18:51.12
Dec. = +24:34:05.16

with an uncertainty of 0.5 arcsec. The OT had r = 18.4 +/- 0.1 mag in 
our first image, brightened to a peak of r ~ 17.6 at ~ 378 s, and then 
faded with a powerlaw decay as F(t) ~ t^-0.94, all calibrated with 
nearby PS1 stars. We thus conclude that the OT is the optical afterglow 
of the burst.
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